1. Field of the Invention
The present invention relates to a facsimile apparatus, control method therefor, and storage medium.
2. Description of the Related Art
There has conventionally been known a technique of transmitting/receiving facsimile data between a transmitting side terminal and a receiving side terminal by facsimile communication with partner terminals via switching equipment. In facsimile communication, first, the facsimile apparatus of the transmitting side terminal captures a telephone line used in facsimile communication. Then, the transmission side facsimile apparatus dials the telephone number of the receiving side terminal serving as a facsimile data transmission destination, and transmits a Calling (CNG) signal.
The CNG signal is a signal which is transmitted first at the start of a facsimile communication procedure by a transmitting side facsimile apparatus. The CNG signal notifies a receiving side terminal that the calling station is a non-voice terminal. When the receiving side terminal includes a facsimile apparatus for facsimile communication and a telephone set for voice communication which is connected to the facsimile apparatus, it can determine, based on the received CNG signal, whether the facsimile apparatus or telephone set is to be used. To make this determination, the receiving side terminal needs to detect the CNG signal passing through the line at high accuracy.
As a technique for detecting a CNG signal in a facsimile apparatus, there has been proposed a technique in Japanese Patent Laid-Open No. 05-244303. In this literature, digital filters are used to detect reception signals in the frequency band of a tonal signal (for example, CNG signal) to be detected and the remaining frequency band. A tonal signal is detected based on the detection states of signals in the respective digital filters. More specifically, when a digital filter corresponding to the frequency (for example, 1,100 Hz) of the CNG signal detects a signal and the remaining digital filters do not detect a signal, the facsimile apparatus determines that the CNG signal has been detected.
The technique in Japanese Patent Laid-Open No. 05-244303 may be unable to properly detect the CNG depending on a reception control method (reception mode) used in a receiving side facsimile apparatus. In general, the facsimile apparatus uses, as reception modes (operation modes), a “TEL answering mode”, “FAX/TEL mode”, and “automatic reception mode”, which will be described later. For example, when the receiving side facsimile apparatus is set in the TEL answering mode, a telephone set which is connected to the receiving side facsimile apparatus and has a recording function executes an off-hook operation and starts recording a signal (voice signal) transmitted from a transmitting side facsimile apparatus. If the receiving side facsimile apparatus detects the CNG signal during recording, it switches the service from the telephone set to the facsimile apparatus, and receives the signal from the transmitting side terminal.
In this case, the telephone set (slave telephone) connected to the receiving side facsimile apparatus often transmits an Outgoing Message (OGM) to the transmitting side facsimile apparatus during recording in the telephone set. The OGM is a series of voice signals transmitted to a partner terminal, and is transmitted using the whole frequency band of the voice signal. When the TEL answering mode is used, the line becomes unclear because the OGM transmitted from the telephone set and the CNG signal transmitted from the transmitting side facsimile apparatus coexist in the frequency band of the voice signal on the line.
It is difficult to appropriately detect the CNG signal by a facsimile apparatus set in the TEL answering mode according to the technique in Japanese Patent Laid-Open No. 05-244303. In the facsimile apparatus, even if a digital filter corresponding to the frequency of the CNG signal detects a signal, a digital filter corresponding to another frequency detects the OGM signal. As a result, no CNG signal can be detected. Hence, the facsimile apparatus cannot properly detect the CNG signal depending on a set operation mode.